This invention relates to a mechanical end stop for a high speed gear train and in particular to an energy absorbing mechanical end stop for a high speed gear train used to drive a variable vacuum capacitor.
Radio transmitters which are capable of broadcasting over multiple bands often require tunable filtering circuits that can be rapidly tuned. An example of one such filtering circuit is that of an antenna coupler that interfaces the output of the radio transmitter with the antenna. This type of filtering circuit must be able to pass energy in the kilowatt range. In general, variable vacuum capacitors are the tuning elements associated with the tunable filters that are tunable and also meet the necessary power requirements. Variable vacuum capacitors are often motor driven and because there is usually a very short period of time to change frequencies, the filtering circuit must be tuned at a high rate of speed. In the case where there is a requirement to go from one extreme of capacitance to another extreme of capacitance such as varying from maximum capacitance to minimum or vice versa, the gear mechanism that is used to interface the motor with the variable vacuum capacitor often has associated with it momentum due to the tuning speeds and usually continues turning after the removal of power from the motor that drives the gear train and varies the capacitance. In the prior art to prevent over driving the capacitor and damaging the variable vacuum capacitor a post was used to stop the gear train at either the upper limit or the lower limit and thus, protect the variable vacuum capacitor. However, the gear train was subject to damaging forces when brought to a sudden and instantaneous stop.